1. Field of the Invention
This invention relates generally to a video display system pattern generating circuit. More particularly, this invention relates to an electronics circuit for generating a fixed test pattern on a cathode ray tube or the like which can be utilized for the testing or repairing of the aforementioned cathode ray tube or the like.
2. Description of the Prior Art
Heretofore, numerous electronic circuits have been employed to produce on a video display system a fixed pattern such that a person may test or repair the video display system. Such circuits are too numerous to discuss herewith. Besides, most thereof constitute prior art devices which are well known to the artisan, thereby obviating the need for further discussion thereof.
Of course, there are several prior art devices which are of some significance, inasmuch as they at least remotely or indirectly concern subject matter that is pertinent to the instant pattern generating circuit.
For example, U.S. Pat. No. 2,741,722 to J. P. Shields discloses a television pattern generator comprising a carrier wave oscillator, means for coupling the oscillator to the antenna input of a television receiver, a high frequency oscillator adapted to operate at multiples of the frequency of the horizontal sweep oscillator in the receiver, and a source of operating voltage. In addition, the aforesaid television pattern generator includes a resistance in series with the voltage source, with the carrier wave oscillator, and the high frequency oscillator, the two oscillators being in parallel with each other, and a gas tube oscillator adapted to be tuned to a frequency which is an even multiple of the vertical sweep oscillator of the receiver and connected to the carrier wave oscillator.
U.S. Pat. No. 2,855,515 to F. R. C. Bernard discloses a television test apparatus comprising a first multivibrator, means to apply a television blanking signal to the first multivibrator to block the same for the duration of the blanking signal and to render the same oscillating between blanking pulse signals, a second multivibrator, and a blanking signal separator coupled between the second multivibrator and the blanking signal applying means to separate the horizontal blanking signal from the vertical blanking signal and render the second multivibrator oscillating between the separated blanking signal pulses. In addition, the television test apparatus includes a combining circuit coupled to both of the aforesaid multivibrators to produce a square wave signal of recurrence rate of one of the multivibrators with phase inversion at twice the recurrence rate of the other multivibrator, and a mixing circuit coupled to the combining circuit and to the blanking signal applying means to interpose blanking signal in the output signal from the combining circuit.
Unfortunately, the aforementioned devices of the prior art ordinarily leave something to be desired, especially from the standpoints of accuracy, efficiency, and complexity in design. In addition, the aforementioned devices of the prior art do not operate in exactly the same manner as the subject invention, and contain a combination of elements that is somewhat different from that of the present invention.